This invention concerns dumpers, typically used to transfer loose parts such as metal fasteners in bulk during various processing steps, particularly in metal finishing operations.
The parts are commonly transported in tote boxes which need to be emptied into an opening of a container used in processing the parts, such as a perforated barrel used in plating, phosphating, etc. Tote boxes are open topped sturdy boxes constructed of metal containers having a metal nose at the front end for directing parts emptied out of the tote box by being tipped forwardly. The filled tote boxes are usually too heavy for manual handling and transferring the contents of a dozen or more tote boxes per hour is typical in any given processing operation. This results in much time being consumed in handling the tote boxes using various lifts.
The parts must be transferred from the tote box into the barrel to begin the finishing process. This transfer can be by dumping the parts directly from the tote box into the barrel, or it can include an intermediate dumping from the tote box into other devices, from which the parts are then fed into the barrel. In either case, it is standard industry practice to use a conventional device called a tote box dumper to automatically dump the parts out of the tote box.
There are many different configurations of tote box dumpers available on the market from companies that specialize in material handling equipment, and their basic method of operation is the same. The tote box is loaded into the hopper of the tote box dumper, where it is constrained in either a passive manner by the configuration of the hopper, or in an active manner by some form of actuated device. The hopper is then rotated about a pivot point by some form of automation, usually hydraulic or electric, which causes the hopper and the tote box within it to be raised and pivoted, tilting the tote box forward in the process. As the tote box tilts forward the parts dump out of the tote box and onto the forward face of the hopper where they slide down toward the barrel opening. The system is always designed such that as the exit nose of the pivoting hopper approaches the opening of the barrel the parts that are sliding down the hopper face enter into the barrel. When the hopper rotates to its maximum practical angle, which is typically about 135°, the exit nose of the hopper protrudes into the opening of the barrel, and all of the parts have theoretically dumped out of the tote box and into the barrel. The tote box dumper then rotates and lowers the hopper and tote box back to their down position. The dumping process is also similar in the case when the material is being dumped into an intermediate device rather than directly into the barrel.
A traditional problem with this dumping process is that for many tote box loads some of the parts do not in fact leave the hopper and/or the tote box when they are dumped. While the magnitude of the problem is dependent on the geometry and quantity of the parts and the configuration of the tote box, it occurs for two primary reasons. First, parts will sometimes become trapped between the front of the tote box and the face of the hopper during the dump process, and then stay in the hopper when it returns to its down position. This happens because the tote box is placed directly up against the front face of the hopper, and when the parts start to dump out of the tote box, the hopper face is often not yet tilted far enough downward to cause the parts to slide toward the hopper exit nose, so the parts instead slide backward toward the bottom of the hopper and get trapped under the tote box. Even when a standoff is used to separate the tote box from the front face of the hopper, some parts can still get trapped. Second, parts will sometimes get caught around the rim or corners of the tote box itself, and then remain in the tote box when it returns to its down position.
For these reasons, the operator needs to continually monitor the dumping process and manually retrieve any parts that were not dumped. If the operator does not notice and remove the retained parts, they could become mixed with a following load of different parts, which then creates the problem of “part mixing” for the customer. In today's quality conscious world, the problem of part mixing has become very important, and a growing number of metal finishing customers are demanding “zero parts per million” mixed parts.
Some commercially available tote box dumpers address the part mixing problem by pivoting the hopper and tote box a full 180° instead of the typical 135°. This orients the tote box completely upside down, which makes it much less likely for any parts to remain in the tote box or to be trapped between the tote box and the hopper walls. Drawbacks to various versions of these dumpers are that they utilize a more complex dual-stage hydraulic mechanism to create the additional rotation, that they require adjustable tote box clamp mechanisms that can restrict part flow, that they require more valuable space above the barrel area, or that they use multiple linkage mechanisms which move the hopper in such a way that it cannot be used to feed the parts directly into a barrel mouth.
An object of the invention is to provide an apparatus and method for dumping loose parts ensuring that all of the parts can be dumped directly into a receiver and to thereby eliminate the problem of part mixing, while not requiring complex bulky apparatus, and tote box clamps.